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Microbiology > WEEK 3 > Flashcards

WEEK 3 Flashcards

1
Q

genome

A

the entirety of an organisms hereditary information. Usually DNA, but an exception is some viruses only have RNA

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2
Q

Human genome

A

22, 000 genes and 3 billion base pairs per genome, two genomes (maternal and paternal) each with 23 chromosomes. So around 6 billion base pairs all together.

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3
Q

bacteriophages

A

viruses that infect bacteria (genome is only 48 000 base pairs)

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4
Q

How many base pairs in E. Coli genome?

A

4.6 million base pairs

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5
Q

How many base pairs in mitochondrial DNA?

A

16 000 base pairs

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6
Q

Why is mitochondrial DNA so small?

A

Some has gone into nuclear DNA also potentially evolution (use it or lose it, the host cell does many things for mitochondria so it needs less functional DNA)

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7
Q

Genome size has nothing to do with…

A

size or complexity! Salamanders have 90 000 million base pairs, clearly we are more complex than salamanders.

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8
Q

The number of protein encoding genes…

A

does not reflect complexity or size of organism either

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9
Q

How much of our genome encodes for protein?

A

1.5%

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10
Q

How much of our DNA is unique and how much of it is repetitive?

A

50-50

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11
Q

What composes repeated sequences of DNA?

A

TRANSPOSONS and REPEATS

. LINEs - long interspersed nuclear elements (more than 500 bp)
. SINEs - short interspersed nuclear elements (less than 500 bp and often highly conserved)
. Retroviral like elements
. DNA only Transposon Fossils

. simple sequence repeats - like GAG repeated hundreds of times
. segmental duplications - thousands of bp (or more) that are repeated

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12
Q

What is unique DNA composed of?

A

. non-repetitive DNA that is neither in introns nor codons - includes promotoers and non-protein encoding genes
. Introns - regions that are spliced out of RNA
. Protein-coding regions - genes that are transcribed and have some protein coding regions

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13
Q

How long is the DNA in each human cell?

A

2 metres unpackaged

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14
Q

Karyotype

A

artificial array of paired chromosomes in a numerical order-diagnostic aid OR you could do chromosome painting hybridization

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15
Q

FISH

A

Fluorescence in situ hybridization

Detects presence of a specific sequence. A probe binds to a target sequence and you see fluorescence.

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16
Q

Chromatin is…?

A

Dynamic. It can be condensed, decondensed, and moved around.

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17
Q

What is each chromosome made of?

A

Each chromosome contains a single, long, linear DNA molecule and associated proteins—called chromatin.

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18
Q

Sister chromatids

A

Two double strands of DNA tied together into one chromosome. Splitting them will create separate chromosomes.

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19
Q

Levels of organization of chromatin

A
  • DNA double helix
  • Nucleosome core particle
  • Nucleosome filament
  • 30 nm fibre
  • Looped domains
  • Metaphase chromosome
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20
Q

How much is DNA compressed in prokaryotes?

A

DNA is condensed through twisting and folding about 1000 X and is complexed with proteins.

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21
Q

Which enzyme is responsible for the supercoiling of DNA?

A

topoisomerase

22
Q

total length of DNA in human body

A

2 x 10^10 km

23
Q

Nucleosome

A

nucleosome core particle + H1 + linker DNA

24
Q

How many times does DNA wrap around core particle?

A

1.8 times, approx. 146 bp

25
Q

How long is linker DNA?

A

Around 80 bp

26
Q

When is DNA decondensed?

A

When genes are being expressed. There is not enough room in the nucleus for everything to be unpacked so only the parts that need to be transcribed are unraveled.

27
Q

Histones

A

Small, positively charged proteins (attract negative phosphates on DNA) that are rich in lysine and arginine.

28
Q

H1

A

like a paperclip; clips DNA onto nucleosome core particle. Necessary for a stable interaction.

29
Q

Four core histone proteins

A

H2A, H2B, H3, and H4

30
Q

What is an octamer core

A

8 protein complex that is found at the centre of the nucleosome core particle. Two of each of the four core histone proteins (H2A, H2B, H3, H4)

31
Q

DNA molecule that has been packaged into a mitotic chromosome is ….. than its extended length

A

10 000 times shorter

32
Q

Cohesion rings

A

involved in making loops of chromatin which are anchored to the nuclear matrix/scaffold.

33
Q

Packing and unpacking DNA requires…

A

ATP

34
Q

Heterochromatin

A

highly condensed (30 nm fibre or even more condensed) chromatin. Usually found at the periphery of the nucleus.

  • meiotic and mitotic chromosomes
  • centromeres and telomeres
  • Barr body
35
Q

Barr body

A

An inactivated X chromosome. One of the X chromosomes in each cell in human females is entirely composed of heterochromatin (half of the cells one is activated in the other half the other is activated).

36
Q

Heterochromatic regions of interphase chromosomes are areas where…

A

gene expression is suppressed

37
Q

Euchromatin

A

relatively uncondensed chromatin, regions where genes tend to be expressed

38
Q

Transcription Factories

A

Regions of the nucleus where you have a lot of substrates and lots of enzymes for transcription.

39
Q

DNA replication is…

A

semi-conservative. Each new daughter cell has one parental strand and one newly synthesized strand.

40
Q

Rules for DNA synthesis

A
  1. DNA is antiparallel
  2. New DNA is synthesized from 5’ to 3’
  3. The template is read 3’ to 5’
41
Q

Where does DNA replication start?

A

Areas rich in As and Ts which are only held together by two hydrogen bonds (less energy to pull apart). Always starts in the same location on DNA, place that is recognized by specific proteins.

42
Q

Origin of replication

A

Where DNA replication starts. Single origin in bacterial DNA but multiple in eukaryotic

43
Q

DNA synthesis is catalyzed by…

A

DNA polymerase

44
Q

dNTPs

A

deoxynucleoside triphosphates; what DNA is synthesized from.

45
Q

NTPs

A

ribonuceloside triphosphates; what RNA is synthesized from.

46
Q

Nucleotides are linked by…

A

phosphodiester bonds

47
Q

Type of DNA growth in many linear viruses

A

Unidirectional growth of single strands from TWO starting points (no lagging strands)

48
Q

Type of DNA growth in some plasmids

A

Unidirectional growth of single strands from ONE starting point (one leading, one lagging strand). Has a replication fork. Leading strand and replication fork go in same direction.

49
Q

Type of DNA synthesis in eukaryotes and some bacteria

A

Bidirectional growth from one starting point. One origin, two replication forks (two leading and two lagging strands).

50
Q

Leading strand is replicated…. while lagging strand is replicated…

A

continuously

discontinuously

51
Q

INGREDIENTS FOR DNA SYNTHESIS

A
  1. Origin of replication
  2. Primers
  3. NTPs
  4. ATP
  5. DNA polymerase
  6. Accessory proteins

Microbiology (10 decks)

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